Tamper resistant closures for finishes of containers have been disclosed, such closures having tear-off bands that are broken away from the main portion of the closure by frangible bridges when the closure is removed from the container.
Such closures for containers are disclosed in U.S. Pat. No. 4,394,918 to Grussen; U.K. 2,022,063; U.K. 1,265,008, 3/1972; U.K. 2,033,350, 5/1980; German DE 30 25 751 Al; French 2,290,114; French 2,241,812, and French 2,490,598.
U.S. Pat. No. 4,394,918 (Grussen), apparently more pertinent to the present invention than the others, discloses a screw cap for a finish of a container, the cap having a depending skirt with an annular tamper indicating band connected by frangible bridges 4 connected thereto. The band has a plurality of tabs or lock-lugs 7 that bend like fishhooks and contact the finish of the container just below the collar 13 of the container neck. The lock-lugs contact the container finish so that when the screw cap is turned for removal, shearing forces cause the bridge 4 to break and leave the band on the container, the lock-lugs 7 being able to resist the compression and shearing forces. When first molded, the lock-lugs 7 are said to be inclined downwardly from the band at an angle (alpha) of about 120.degree. to 140.degree. and when the cap is screwed on the container, the lugs bend to define an acute angle (beta) of, for instance, 40.degree. to 60.degree..